While methods exist for evaluating nonuniformity of pulmonary function, present indices use only a very small amount of the information potentially available in well performed washout studies. This project seeks to improve methods for studying ventilation and diffusion nonuniformity and the distribution of inspired gas. Washout of tracer gases will be analyzed using mass spectrometer. Computer techniques will be sought to carry out a continuous analysis. Tests developed will be applied to healthy human subjects enrolled in a longitudinal study so as changes in lung function. Test will also be applied to patients changes in lung function. Tests will also be applied to patients with various well characterized lung diseases to evaluate the diagnostic ability of the tests.